1. Field of the Invention
The present invention relates to wireless security sensor systems and, more particularly, to wireless security sensor systems, for installation in doors and/or windows, of the type employing RF transmitters for emitting radio frequency signals.
2. Description of the Related Art
Wireless security systems allow a residence or business to be monitored without a need for extensive wiring throughout the residence or building, and therefore have the advantages that they require lower installation costs and lower product costs and provide an easier upgrade path for possible future improvements than prior systems requiring such wiring.
Prior wireless security sensor systems communicate a disturbance to a master station or a controller and monitor, typically located within the same building as the wireless security system, on a common radio frequency and usually comprise a housing containing a battery, a microprocessor, an RF transmitter and an antenna. These prior systems are designed to be installed into a building after the construction of the building has been completed, by being mounted on the surface of a window sash or door or by drilling into a door or door frame.
In order to provide a sufficient transmission range, to report reliably to the master station or controller, the components within the housing, and in particular the antenna, must be of sufficient size. Consequently, the housing is bulky and, when surface mounted, is clearly and unattractively visible. When a sufficiently lengthy hole is required to be drilled into a door frame to accommodate the housing, there is a risk of defects such as water damage.
It is accordingly an object of the present invention to provide an improved wireless security sensor system employing a sensor unit having a substantially more compact housing than has previously been possible and which, therefore, presents a substantially less intrusive appearance than prior alarm sensor units.
According to the present invention, there is provided an wireless security sensor system which comprises a frame defining a opening, with closure movable relative to the frame between open and closed positions. A sensor unit is embedded in the frame comprises and a housing having an inner end within the frame, an outer end at the opening and an antenna extending from the housing at the exterior of the housing. The housing also contains a sensor switch, a microprocessor, and RF transmitter and a battery. A magnet is mounted in the closure for actuating the sensor switch.
Since the antenna does not have to be accommodated within the housing, the housing can be made substantially smaller than has been possible with prior art alarm sensor unit housings. Therefore the sensor unit can be almost entirely embedded in, for example, a window sash or frame or in a small boring in a door. Consequently, the sensor unit can be so effectively concealed that it is not only unobtrusive but effectively almost invisible.
The use of a wire antenna has the further advantage that it enables the sensor unit to be designed so as to conserve power and therefore so as to require smaller batteries than have been required in prior art sensor units.
Preferably, the antenna is in the form of a flexible wire, which can be conveniently bent, as required, in order to adapt it to the frame.
The frame may be a window frame or a door frame, the closure correspondently being a window sash or a door.
The frame may, for example, be in the form of an extrusion, for example a vinyl extrusion, having a hollow interior. In that case, the wire can be positioned, during the installation of the sensor unit into the frame, so that the antenna extends longitudinally along the hollow interior of the frame.